Author: Bae, S.
Paper Title Page
THP010 Analysis of Beam Stability in the KAERI Ultrashort Pulse Accelerator 697
  • H.W. Kim, S. Bae, B.A. Gudkov, K.H. Jang, Y.U. Jeong, Y. Kim, K. Lee, S.V. Miginsky, J. Mun, S. H. Park, S. Park, N. Vinokurov
    KAERI, Daejon, Republic of Korea
  • K.H. Jang, Y.U. Jeong, H.W. Kim, K. Lee, S.V. Miginsky, S. H. Park, N. Vinokurov
    UST, Daejeon City, Republic of Korea
  • S.V. Miginsky, N. Vinokurov
    BINP SB RAS, Novosibirsk, Russia
  An RF-photogun-based linear accelerator for the Korea Atomic Energy Research Institute (KAERI) ultrashort pulse facility is under construction. It has a symmetry structure with four different beamlines. The UED beamlines will generate ultrashort electron pulses with over 106 electrons per pulse for the single-shot measurements on femtoseconds dynamics of atomic or molecular structures. Electron bunches with an energy of ~3 MeV from the RF photogun can be compressed up to less than 50 fs by achromatic and isochronous bends. The intrinsic r.m.s. timing jitter of the pulses through the bends is estimated to be less than 30 fs with the r.m.s. energy fluctuation of 0.1%. In the THz pump and X-ray probe beamline, two successive laser pulses with a time interval of ~10 ns are used to generate two electron bunches having bunch charges more than 100 pC. Two electron bunches are accelerated by a linac up to ~25 MeV and separated into individual beamlines by a fast kicker. We will present on estimated timing jitter and effects of magnet errors to the beam dynamics in the accelerator by considering beam dilution effects.  
Development of an S-band Cavity-type Beam Position Monitor for a Table-top Terahertz Free-electron Laser  
  • S.Y. Noh, E.-S. Kim
    Kyungpook National University, Daegu, Republic of Korea
  • S. Bae, K.H. Jang, Y.U. Jeong, H.W. Kim, K. Lee, J. Mun, S. H. Park, N. Vinokurov
    KAERI, Daejon, Republic of Korea
  A cavity-type beam position monitor (BPM) has been developed for a compact terahertz (THz) free-electron laser (FEL) system and ultrashort-pulsed electron linac system at the Korea Atomic Energy research Institute (KAERI). The cavity-type BPM has higher sensitivity and faster response time even at low charges, comparing with other types of BPMs. The designed position resolution of the cavity BPM is less than 10 μm. The material of the BPM is aluminium and the vacuum could be kept by indium sealing without brazing process, which result in easy modification and saving cost. The resonance frequency of the cavity BPM is 2.801 GHz and has a dimension of 200 x 220 mm (length x height) with a pipe radius of 38 mm. When electron beam passing through the cavity BPM with an offset, the amplitude of a dipole mode which depends linearly on the beam offset inside the cavity BPM is excited. With the KAERI THz FEL, signals from the BPM was measured by using an oscilloscope as a function of the beam offset. The position sensitivity was calculated to be 6.19 mV/mm/mA. By measuring the thermal noise of the system, position resolution of the cavity BPM was estimated to be less than 1 μm.